20 watt fluorescent lamp

ABSTRACT

Luminous flux and luminous efficiency of a 20 watt fluorescent lamp comprising a ballast specified by the I.E.C. Publication 82 (covering Ballast for fluorescent lamps) is greatly improved by employing an improved tube characterized by: HAVING A NOMINAL TUBE LENGTH OF 590 MM AND AN INNER DIAMETER OF 20 MM TO 25 MM, PROVIDED INSIDE EACH END OF THE TUBE WITH AN ELECTRODE E having a length l of 15 mm to 55 mm inward (from the end face of each cap C as measured as shown in FIG. 2,) and containing mixed rare gas inside the tube, the rare gas having a composition ratio represented by any point within a diagonal region defined by connecting the following points (a) to (e) and (a) with straight lines in the following order, on a trilinear chart for xenon, krypton and argon mixture: (A) Xe: 2%, Kr: 0%, A:98% (b) Xe:15%, Kr: 0%, A:85% (c) Xe:15%, Kr:65%, A:20% (d) Xe:0%, Kr:80%, A:20% (e) Xe:0%, Kr:10%, A:90%, the pressure of the mixed gas being between 1.0 mmHg and 3.5 mmHg at a temperature of 20* C.

United States Patent [191 Otsuka eta].

[ 11 Dec. 18, 1973 1 20 WATT FLUORESCENT LAMP [75] inventors: Hitoshi Otsuka, Hirakata; Kazumasa Nohmi; Masao Hommo, both of Takatsuki City, all of Japan [73] Assignee: Matsushita Electronics Corporation,

Kadoma City, Osaka, Japan 122 1 Filed: Nov. 7, 1972 21 Appl. No.: 304,419

130] Foreign Application Priority Data Primary Examiner-Paul L. Gcnsler A!t0rneyE. F. Wenderoth et a1.

[57] ABSTRACT fluorescent lamp comprising a ballast specified by the I.E.C. Publication 82 (covering Ballast for fluorescent lamps) is greatly improved by employing an improved tube characterized by:

having a nominal tube length of 590 mm and an inner diameter of 20 mm to 25 mm, provided inside each end of the tube with an electrode E having a length l of 15 mm to 55 mm inward (from the end face of each cap C as measured as shown in FIG. 2,) and containing mixed rare gas inside the tube, the rare gas having a composition ratio represented by any point within a diagonal region defined by connecting the following points (a) to (e) and (a) with straight lines in the following order, on a trilinear chart for xenon, krypton and argon the pressure of the mixed gas being between 1.0 mmHg and 3.5 mmHg at a temperature of 20 C.

6 Claims, 3 Drawing Figures 589.8mmAT MAXIMUM ib' 1 C) I I m J- +594. 5 TO 596 9mm 60.4mmATMAX1MUM 20 WATT FLUORESCENT LAMP BACKGROUND OF THE INVENTION This invention relates to a 20 watt fluorescent lamp, and especially to an improvement in fluorescent tubes of 20 watts and has as its purpose to provide improved luminous flux and efficiency of the tube and reduction in the cost, compared with conventional 20 watt flucrescent tubes.

As is well known, fluorescent lamps are widely used in our present livelihood, and especially those of 20 watts are commanding a tremendous market. However, in general, the 20 watt fluorescent tubes of the prior art are manufactured in accordance with the dimensions of the I.E.C. (International Electrotechnical Commission) Publication 81 (for Tubular fluorescent lamps for general lighting service), namely, with a nominal tube length of 590 mm and an outer diameter of 38 mm, containing inside about 2 to 3 mmHg of argon gasand some quantity of mercury, fitted with an electrode at each inner end, and sealed with a metal cap at each outer end. I

Further characteristics of the conventional 20 watt fluorescent lamp in current general use are as follows. As shown in FIG. 1, the lamp comprises a ballast B, a glow starter G and a 20 watt fluorescent tube T. For the ballast B, a choke coil type ballast as specified by the I.E.C. Publication 82 (covering Ballasts for fluorescent lamps) is employed. Such ballast is hereinafter referred to as conventional ballast or ballast in current use.

SUMMARY OF THE INVENTION The inventors of the present invention made thorough investigations for improving the luminous flux and efficiency of a fluorescent lamp using said 20 watt fluorescent fitting-and-ballast and for reducing the cost of the tube. Consequently, the inventors found that a fluorescent tube with a specified inner diameter of the bulb, electrodes of a specified length and enclosed gas ofa specified composition ratio, showed good performance.

BRIEF EXPLANATION OF THE DRAWING FIG. 1 is a diagram showing a general construction of a lamp with a 20 watt fluorescent tube, of the prior art as well as of the present invention.

FIG. 2 is a partially cut away side view of a 20 watt fluorescent tube of the present invention, and

FIG. 3 is trilinear chart showing the composition of mixed gas enclosed in the fluorescent tube.

DETAILED DESCRIPTION OF THE INVENTION As a result of the investigations, a 20 watt fluorescent lamp of superior performance has been invented, wherein the fluorescent tube is characterized by:

having a nominal tube length of 590 mm, i.e., as specified for a 20 watt fluorescent tube in the I.E.C. Publi cation 81, and an inner diameter of 20 mm to 25 mm,

having inside each end of the tube an electrode E having a length lof mm to 55 mm inward from the end face of each cap C as measured shown in FIG. 2,

and containing mixed rare gas inside the tube, the rare gas having a composition ratio represented by any point within a diagonal region defined by connecting the following points (a) to (e) and (a) with straight lines in the following order, on a trilinear chart for xenon, krypton and argon mixture:

(a) Xe: 2%. Kr: 0%. mam (h) Xc:l5%, Kr: 0%. M8594 (c) xt-nsa, Kr:65%, mzw a Xe: 0%. Kr:s0%. A:2l)% (e) Xe: 0%, KrzlU'lh, A:9()t,

the pressure of the mixed gas being between 1.0 mmHg and 3.5 mmHg at a temperature of 20 C.

FIG. 3 shows the trilinear chart indicating the diagonal regions.

Namely, by applying said fluorescent tube to a conventional 20 watt fitting and ballast in current use, which isspecified by the I.E.C. Publication 82, and lighting it a luminous flux of between 1,250 lm (lumens) and 1,350 lm is obtainable, in comparison with 1,200 1m obtainable with a conventional 20 watt fluorescent tube, that is, an increase of 4. 15 to 12.5 percent in the luminous flux quantity. The electric power consumption of this new fluorescent tube is 17 watts to 18 watts, which is l0to 15 percent less than the power consumption of 20 watts of the conventional 20 watt fluorescent tube. Consequently, the lamp efficiency of the fluorescent tube of the present invention becomes lm/w to 79 lm/w, as compared with 60 lm/w for the conventional 20 watt tube, that is, an increase of 16.7 percent to 31.7 percent in the lamp efficiency.

The reason for the attainment of such a tremendous improvement is that by using the fluorescent tube of this invention having the abovementioned inner diameter, the length of the electrode inward from the end face of the cap C, the composition of enclosed gases and their pressure, respectively selected within the abovementioned ranges, with a conventional 20 watt fluorescent fitting-and-ballast, the loss by the selfabsorption of the resonance radiation line of mercury and the electrode wattage loss are both alleviated, thus enabling the attainment of improved luminous flux and lamp efficiency.

To explain further the details of said lamp, in consideration of the fluctuation of lamp luminous flux due to the variation of manufacturing conditions of fluorescent tubes, the inner diameter that affords distinctly superior luminous flux as compared with the conventional 20 watt fluorescent tubes is one smaller than 25 mm. Nevertheless, when the inner diameter becomes smaller than 20 mm, starting of the lamp with the conventional 20 watt fluorescent fitting-and-ballast becomes difflcult.

Increases in the composition ratios of xenon and krypton are very effective for preventing damage to the electrodes and afford desirable results for the life of'the Y lamp. This is due to the fact that increases in the composition ratios of xenon and kryptonreduce the cathode fall potential and alleviate the electrode sputtering by ion bombardment. On the other hand, in the case of xenon-krypton-argon mixed gas, if the volume ratio of xenon exceeds 15 percent, the luminous flux and efficiency of the lamp distinctly decrease; likewise, if the volume ratio of krypton exceeds 80 percent, the luminous flux distinctly decreases and its superiority to the conventional 20 watt fluorescent tubes will be lost.

In case the composition ratios of both krypton and xenon are small so, that'the point on the trilinear chart is out of the diagonal region toward point A representing percent argon, the lamp voltage increases, making the lamp starting with a conventional 20 watt fluorescent fitting-and-ballast difficult. The electrode length 1, namely, the length from the tube end to the inward edge of the electrode as shown in FIG. 2, is one of the important factors affecting the performance, so much so that the fluorescent tube of this invention characterized by the abovementioned combinations of the inner diameter, kinds of enclosed gases and the pressure can function with the conventional 20 watt fluorescent fittingand-ballast only when provided with a pair of electrodes conforming to the dimensional range of length l.

The fluorescent tube according to this invention having the nominal tube length of 590 mm combined with the inner diameter, as well as the enclosed rare gas compositions and pressure, all selected within the above-described ranges, was applied to a conventional 20 watt fluorescent fitting-and-ballast and lit, and many experiments were made for various electrodes of different length l, and consequently, the following result was obtained. Namely, the lamp starting became easier the longer the electrode length I. Also, the difference of the electrode length l affects the luminous flux, which be comes the largest with an electrode length l of 28 mm, but if the length l exceeds 55 mm, the luminous flux falls to the same level as, or even lower than, that of the conventional fluorescent tube.

Actual examples of this invention will be described as follows.

EXAMPLE 1 A fluorescent tube having a length of 588.8 mm measured from one base face to another base face, an inner diameter of 22.5 mm, an electrode length l of 40 mm (i.e., the length from each tube end inward to each electrode coil inside the tube as shown in FIG. 2), containing inside rare gas at 2.3 mmHg (at 20 C) which was a mixture of xenon, krypton and argon gases in the volume ratios of 4 percent, 45 percent and 51 percent,

I respectively, and some quantity of mercury, and coated on the inner wall with 5.9 g/cm of antimonymanganese-activated calcium halophosphate phosphor, was applied to a conventional 20 watt fluorescent fitting-and-ballast to constitute a lamp. This lamp, when lit, had a luminous flux of 1,300 lm, an electric consumption of 17.5 watts, a current of 360 milliampere and a lamp voltage of 58 volts, resulting in a lamp efficiency of 74.3 lm/w. These results show the tremendous improvements as compared with a conventional 20 watt tube having a luminous flux of 1,200 lm, an electric consumption of 20 watts, and a lamp efficiency of 60 lm/w.

EXAMPLETZ A fluorescent tube having a tube length of 588.8 mm measured between base faces, an inner diameter of 22.5 mm and an electrode length l of 40 mm, containing inside rare gas at 2.0 mmHg (at 20 C) which is a mixture of xenon and argon gases in volume ratios of 8 percent and 92 percent, respectively, and some quantity of mercury, and coated on the inner wall with 5.9 g/cm of antimony-manganese-activated calcium halophosphate phosphor, was applied to a conventional 20 watt fluorescent fitting-and-ballast to constitute a lamp. This lamp, when lit, had a luminous flux of 130 Im, an electric consumption of 17.4 watts, a lamp current of 365 milliampere, a lamp voltage of 57 volts, resulting in a lamp efficiency of 75.9 lm/w and proving to be a distinct improvement over a conventional 20 watt fluorescent tube in respect of the luminous flux and the lamp efficiency.

EXAMPLE A fluorescent tube having a tube length of 588.8 mm, measured between base faces, an inner diameter of 22.5 mm, an electrode length I of 35 mm, containing inside rare gas at 2.2 mmHg (at 20 C) which is a mixture of krypton and argon gases in volume ratios of 52 percent and 48 percent, respectively, and some quantity of mercury, and coated on the inner wall with 5.9 g/cm of antimony-manganese-activated calcium halophosphate phospher, was applied to the conventional 20 watt fluorescent fitting-and-ballast to constitute a lamp. The above lamp, when lit, had a luminous flux of 1,280 Im, an electric consumption of 17.8 watts, a lamp current of 355 milliampere and a lamp voltage of 60 volts, resulting in a lamp efficiency of 72 lm/w and proving to be a distinct improvement over the conventional 20 watt fluorescent tube in respect of the luminous flux and the lamp efficiency.

EXAMPLE 4 A fluorescent tube having a tube length of 588.8-mm, measured between base faces, an inner diameter of 22.5 mm, an electrode length l of 10 mm and enclosed rare gas consisting of xenon 4 percent, krypton 45 percent, argon 51 percent (P2.3 mmHg) and some quantity of mercury was applied to a conventional 20 watt fluorescent fitting-and-ballast to form a lamp and was lit. There was no problem while the environmental temperature was above 0 C, but when the temperature went down, the starting of the lamp got difficult, and at an environmental temperature of, for instance, l0 C, full starting of the lamp required 102 percent of the rated source voltage, but '100 percent of the rated source voltage with an electrode length l of 15 mm. It the electrode length l exceeds 55 mm the luminous flux decreases.

The 20 watt fluorescent tube according to the present invention attains distinct improvements in the lamp luminous flux and efficiency. Furthermore, whereas the durability of this new fluorescent tube is just as good as that of the conventional fluorescent tubes, its economical advantages are incomparable due to its reduced diametral size, resulting in a saving in the costs of raw material, packing, transportation, storing, and so forth.

As described above, the fluorescent tube of the present invention, when combined with a conventional 20 watt fluorescent fitting-and-ballast, embodies many advantages through the improvements in the luminous flux and efficiency, as well as a reduction in cost, and thereby offers a great industrial contribution. Therefore, the inventors hereof make the following claims for patent.

What is claimed is:

1. A fluorescent lamp comprising a fitting and a ballast for a standard 20 watt fluorescent tube, and a fluorescent tube comprising: a tubular glass bulb the inner wall of which-is coated with a fluorescent layer, a cap with connecting pins on each end of said bulb, the tube having a length of about 590 mm, an electrode on each end of the glass bulb, enclosed mixed rare gas and mercury inside the bulb,

the glass bulb having an inner diameter of between 20 and 25 mm, each electrode having a length of between 15 and 55 mm as measured from the end face of the cap to a coil of the electrode, the enclosed mixed rare gas having a composition ratio represented by any point within a diagonal region defined by connecting the following points (a), (b), (r), (d), (1'), and (a) with straight lines in this order, on a trilinear chart for xenon, krypton and argon mixture:

(22) Xe: 2%, Kr: A: 98% (h) Xc: I5%, Kr: 0'7, A: 85% (1:)Xc: Kr: 65%, A: a X0: 0%, Kr: 80%, A; 20% (c) Xc: 0%, Kr: 10% A: 90%,

the pressure of the mixed gas being between 1.0

mmHg and 3.5 mmHg at a temperature of 20 C.

2. A fluorescent lamp according to claim 1 wherein the mixed rare gas consists of krypton and argon.

3. A fluorescent lamp according to claim 1 wherein the mixed rare, gas consists of xenon and argon.

4. A fluorescent tube for use in a fluorescent lamp having a fitting and a ballast for a standard 20 watt fluorescent tube, saidfluorescent tube comprising a tubular glass bulb the inner wall of which is coated with a fluorescent layer, one cap with connecting pins on each end of said bulb, the tube having a length of approximately 590 mm, one electrode on each end of the glass bulb, enclosed mixed rare gas and mercury inside the bulb,

said glass bulb having an inner diameter of between 20 and 25 mm,

each electrode having a length of between 15 and 55 mm as measured from the end face of the cap to a coil of the electrode,

the enclosed mixed rare gas having a composition ratio represented by any point within a diagonal region defined by connecting the following points (a), (b), (c), (d), (e), and (a) with straight lines inthis order on a trilinear chart for xenon, krypton and argon mixture:

mmHg and 3.5 mmH gat a temperature of 20 C.

5. A fluorescent tube as claimed in claim 8 wherein the mixed rare gas consists of krypton and argon.

6. A fluorescent lamp as claimed in claim 8 wherein the mixed rare gas consists of xenon and argon. 

2. A fluorescent lamp according to claim 1 wherein the mixed rare gas consists of krypton and argon.
 3. A fluorescent lamp according to claim 1 wherein the mixed rare gas consists of xenon and argon.
 4. A fluorescent tube for use in a fluorescent lamp having a fitting and a ballast for a standard 20 watt fluorescent tube, said fluorescent tube comprising a tubular glass bulb the inner wall of which is coated with a fluorescent layer, one cap with connecting pins on each end of said bulb, the tube having a length of approximately 590 mm, one electrode on each end of the glass bulb, enclosed mixed rare gas and mercury inside the bulb, said glass bulb having an inner diameter of between 20 and 25 mm, each electrode having a length of between 15 and 55 mm as measured from the end face of the cap to a coil of the electrode, the enclosed mixed rare gas having a composition ratio represented by any point within a diagonal region defined by connecting the following points (a), (b), (c), (d), (e), and (a) with straight lines in this order on a trilinear chart for xenon, krypton and argon mixture: (a) Xe: 2%, Kr: 0%, A: 98% (b) Xe: 15%, Kr: 0%, A: 85% (c) Xe: 15%, Kr: 65%, A: 20% (d) Xe: 0%, Kr: 80%, A: 20% (e) Xe: 0%, Kr: 10%, A: 90%, the pressure of the mixed gas being between 1.0 mmHg and 3.5 mmHg at a temperature of 20* C.
 5. A fluorescent tube as claimed in claim 8 wherein the mixed rare gas consists of krypton and argon.
 6. A fluorescent lamp as claimed in claim 8 wherein the mixed rare gas consists of xenon and argon. 